Episode #1.3 - S1-E3
Continuity mistake: Poirot is talking to the owner of Twinkle Toes and confirms that indeed the victim was strangled with his merchandise. The man listens with his fingertips adjoined and pointed towards Poirot, but when it cuts to his response ("Poor kid") his left hand is partially in frame and in a different position altogether. (00:17:50)